Air quality is a major concern worldwide, particularly in urban areas, due to its direct consequences on human health. In the political agenda, air quality issues can be coupled with climate change mitigation policies since many actions aimed at air quality improvement (such as reducing fossil fuel combustion) involve a concurrent reduction of GHG emissions. NBS based on the creation, enhancement, or restoration of ecosystems in human‐dominated environments also exploit the synergy between ecosystem processes that regulate pollutants and CO2 in the atmosphere. Vegetation affects air quality mainly through the removal of air pollutants (PM10, NO2, O3, CO, SO2) through dry deposition, although certain species can also emit biogenic volatile organic compounds (BVOC), which are ozone precursors. However, vegetation can also reduce the air temperature, which reduces the emission of BVOCs and slows down the creation of secondary pollutants such as ozone (Wang et al., 2015b; Calfapietra et al. 2013). Despite their limited contribution compared to the overall production of pollutants and GHG emissions at the city level, measures to tackle air quality by enhancing green infrastructure can be considered a good investment due to the number of co‐benefits that they produce and their contribution to amenity value over time (Baró et al., 2015).

A number of co‐benefits both for the outdoor (e.g. stormwater retention) and for the indoor environment (i.e., reduced energy needs and a more pleasant environment due to the higher thermal and noise insulation) (Wang et al., 2016).

Maintaining existing green infrastructure (Davies et al., 2011).

A wide range of co‐benefits including shading, water retention, dry precipitation, infiltration.

Examples of indicators for assessing the impact of the above mentioned actions are listed on p.24 of the report